

A238336


The first row of Pascal's triangle having exactly n distinct squarefree numbers, or 1 if no such row exists.


1



0, 2, 5, 7, 13, 11, 15, 44, 53, 46, 59, 23, 43, 278, 191, 143, 79, 119, 187, 62, 47, 221, 214, 1643, 159, 238, 95, 473, 314, 3583, 671, 474, 958, 3071, 5719, 215, 1439, 7423, 1663, 447, 223, 3695, 4346, 4318, 12983, 319, 35069, 5983, 5471, 8567, 959, 3067
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..52.
A. Granville and O. RamarĂ©, Explicit bounds on exponential sums and the scarcity of squarefree binomial coefficients, Mathematika 43 (1996), 73107, [DOI].


MATHEMATICA

nn = 20; t = Table[1, {nn}]; found = 0; n = 1; While[found < nn, n++; len = Length[Select[Binomial[n, Range[0, n/2]], SquareFreeQ[#] &]]; If[0 < len <= nn && t[[len]] == 1, t[[len]] = n; found++]]; t


CROSSREFS

Cf. A064461, A238337.
Sequence in context: A041975 A042577 A092792 * A083271 A094285 A121218
Adjacent sequences: A238333 A238334 A238335 * A238337 A238338 A238339


KEYWORD

nonn,more,hard


AUTHOR

T. D. Noe, Mar 05 2014


EXTENSIONS

Extended by T. D. Noe, Mar 07 2014


STATUS

approved



